Motion picture apparatus



July 30, 1940. F. LEVENTHAL MOTION PICTURE APPARATUS Filed May 19, 1938 ATTORNEYS Ratente d Jujly 30, 1940 UNITED STATES MOTION PICTURE APPARATUS Jacob F. Leventhal, ,New York, N. Y., as'signor to. Leventhal Patents, Inc., New York, N. Y., a cor-' poration of Delaware Application May 19, 1938, Serial No. 208,'i40 8Claims. (oi. 88 16.8)

This invention relates to motion picture apparatus and more especially to an optical compensating system for producing stationary images of pictures on a film advanced at a uniform rate 5 of speed. i

In certain types of motion picture projection,

such, for example, as projection of a motion pic- 'ture image that is to be televised, a pictureimage frequency which is a multiple of 60 per second (the standard A C. frequency) is necessary if objectionable effects are to be avoided. The

standardmotion picture frequency is 24 per second. i

e v An object of this invention is an optical convpensating system which is effective to produce a picture image frequency of 60 per second from a film uniformly advanced at the rate of 24 pictures per second.

According to this invention, the film is uniforinly fed at the rate of 24 pictures per second and is optically compensated in stages in a manner similar to that disclosed in the U. S. patent to Jacob F. Leventhal, No.11,974,5'73. The compen'sating arrangement is such that alternate pictures on.the film are compensated two and three timesrespectively. Thus, of 24 pictures 12 will be compensated twice and 12 will be compensated thrice, thereby producing the desired frequency of 60 picture images per second. As

the compensation cycles are-of equal duration, it is evident that one picture will be exhibited for a longer time than its successor, or vice versa.

Other objects, novel features and advantages of this invention will become apparent from the 5following specification and accompanying drawing, wherein: I

Fig. 1 is a diagrammatic section of apparatus embodying the invention;

Fig. 2 is a section substantially on the line 2 0! F18- 1, and Fig. 3 illustrates agrammatically the various images produced by the compensator during two successive picture cycles.

' In the drawing, I0 is a light source and II is a condenser lensassociated therewith to direct light from the source through the film gate l2,

bringing the light to focus on a screen II constituting part of a television transmitter which forms no part of the present invention and which is scanned'at a frequency of cycles pr second.

An optical compensator 14 consisting of a single glass platels rotatably mounted-just beyond the film gate and an obturator 15 is rotatablymounted in position to intercept the light beam between the compensator and the screen. A four picture sprocket l8 co-operates with a retaining roller IT to draw a, film l8 past the gate ii. The compensator speed is five times that of the sprocket l6 and this timing is maintained by the five to one gears l9 and it connected respectively 5 to thesprocket l6 and the compensator it. The shutter or obturator 15 rotates at twice the speed of the sprocket wheel l6 and this timing is maintained through the gear train 2|, 22 and 23, the shaft for the gear 23 being driven by a motor 24 10 through suitable belt and pulleys. The compensator thus makes five revolutions for each four pictures and as each compensating stage requires one-half revolution, there are five compensating stages for two picture cycles or movement of the film a distance equal to two frames. Also, the obturator l5 makes one complete revolution for a series of 'five compensations. Be-

tween the compensator and the obturator are arranged a series of five lenses L1, L4, L2, L5 and 20 La in the direction of film travel and the obturator is provided with five slots S1, S2, S3, S4. and S5 arranged at the proper radial distance to register respectively wlththe lenses L1, In, L3, L4, Ls. Between successive slots are provided 25 blank spaces which interrupt the passage of light to the screen It a I v The rotation of the compensator through 180 constitutes one compensation cycle. Compensation does not take place throughout the whole 30 cycle but only for a selected portion starting with the compensator about as shown and ending when it has reached an equal and opposite angular position. The extent of the compensating period is determined by the length of the 35 slots and the obturator interrupts the light over the remainder of the period.

I The thickness of the'compensator l4 and its index of refraction are such as to produce during compensation a stationary virtual imageof the 40 j film picture.- For simplicitys sake, merely a single point 0 .will be considered, such point being the geometrical center of the picture.

During the. movement of one picture through a distance equal to three compensating cycles, 45 three virtual images I'v I'v and Y1 will be produced and simultaneously with the production of each of these'images, the slots 81; Si and S: will register with the lenses L1, L: and

L; respectively, thus producing three successive 5o registering images on the screen I 3. During additional movenient of the film through a distance equal to two' more compensating cycles, additional virtual images 1.,, .1v,- .wm be formed, which, however, lie outside the projection field and-so are not re-imageable as a practical matter ,on the screen. However, virtual images I"v and I"v are formed in the projection field of the corresponding point on the succeeding picture and simultaneously with the production of these images, the slots S4 and S register with-the lenses L4 and L5 to re-image said virtual images on the screen l3. Also during the first three compensating stages, the images I"v ,.I"v and I"v, of the center point 0 of tha second picture are produced simultaneously with the images 'Iv I't, and I'v but lieoutside the projection field and so are not re-imageable.

In Fig. 3, "are indicated the relationships of the various images produced during two picture cycles. The usable images or those lying -within the projection field are identified in heavy lines, while the non-usable images or those lying outside'the projection field are identified by light lines. Since a picture image is produced on the screen l3 for each compensation stage, it is apparent that the above described arrangement, will produce 60 images for each 24 film pictures and as the-film is fed. at the rate of 24 pictures per second, the frequency of the picture images produced on the screen l3 will be 60 per second.

In the case of standard film, the distance of two frame heights is 1.5 inches. The space between the virtual image points is .300 inch. Each virtual image point of one film has a counter part for the succeeding frame exactly .750 inch or one frame height away. Since the five compensations relate to two successive pictures, it is apparent that Iv will lie on the optical axis with vI" and Iv symmetrical thereto, while. the images I'v and I means for feeding framed motion picture film at uniform linear speed, a rotatable optical compensator operable to produce a stationary'image of said film, means connecting said feeding means and compensator to effect; during movement of the film through N picture frames movement of the compensator through 2N+1 compensating cycles, whereby the geometrical center of one frame of the moving film is rendered optically conjugatesuccessively with each of N+1 stationary spaced points in the direction of film traveland the geometrical center ofthe succeeding picture is rendered opticallyconjugate with each of, two 'N stationary spaced points in the direction of film travel, 2N+1 lenses individually related to said spacedpoints and arranged to render optically conjugate said spaced points and a single stationary point, and means timed with the compensating means for rendering each lens efiective only during its related compensating'cycle.

2. A motion picture apparatus comprising means for feeding framed motion picture film at uniform linear speed, a rotatable optical compensator operable to produce a. stationary image of said film, means connecting said feeding means and compensator to eflect, during movement of the film through N picture frames movement of the compensator through 2N- |-1 compensating cycles, whereby the geometrical center of one framed the moving film is rendered optically conjugate successively with each of N+1 stationary spaced points in the direction of film travel and the geometrical center of the succeeding picture is rendered optically conjugate with each of sator operable to produce a stationary image of I said film, means connecting said feeding means and compensator-to, efiect, during movement of the film through two N picture frames move ment of the compensator through five compensating cycles, whereby the" geometrical center of I one frame of the moving film is rendered opti--( cally conjugate successively with each of three stationary spaced points in the direction of film travel and'the geometrical center of the succeed ing picture is rendered optically conjugate with each of two stationary spaced points in the direction of film travel, five lenses individually related to said spaced points and arranged to render optically conjugate said spaced points and-a single stationary point, and means timedwith the compensating means for rendering each lens effective only during its related compensating cycle.

4. A motion picture apparatus comprising means for feeding framed motion picturmfilin at uniform linear speed, a rotatable optical compensator operable to produce a stationary image of I said film, means connecting said feeding means andcompensator to effect, during movement of the film through two picture frames movement of the compensator through five compensating cycles, whereby the geometrical center of one frame of the moving film is rendered optically conjugate successively with each of three stationary spaced points in the direction of film travel and the geometrical center of the succeeding picture is rendered optically conjugate with each of two stationary spaced points in the direction of film travel, five lenses individually related to said spaced points and arranged to render optically conjugate said spaced points and a single stationary point, and an obturator rotated at speed of one rotation for each picture cycle, said obturator having five .light transmitting slots ar ranged to register one with each lens. A

5. A motion picture apparatus comprisin means for feeding framed motion picture film at uniform linear speed, a rotatable optical compensator arranged and adapted upon movement through 2N+1 compensating cycles in timed relatmnwith movement of the film through N picimage plane, each of said imagingmeans being individual to oneof said spaced images, and means synchronized 'with said optical compensating means for rendering inefi'ective all but one of said imaging means during each compensation cycle.

Q. A motion picture apparatus" comprising 7 means for feeding framed motion picture film at uniiorm linear speed, a rotatable optical compensator arranged and adapted upon movement through five compensating cycles in timed relation with movement of the film through two picture frames to produce three successive stationary spaced images of a picture and two successive stationary s'paced images 01 the succeeding picture,v five imaging means for re-imaging said spaced images in registering alinement in a common image plane, each said imaging means being individual to one ofsaid spaced images, and

means synchronized with said optical compensating means for rendering inefiective all but one of said imaging means during each compensation cycle.

7. A motion picture apparatus comprising means for feeding framed motion picture film at uniform linear speed, a rotatable optical compensator arranged-and adapted upon movement through 2N+1 compensating cycles in timed relation with movement of the film through N picture frames to produce N+1 successive stationary spaced images of a picture and N successive stationary spaced images of succeeding pictures, 2N+1 imaging means for re-imagingsaid spaced images in registering alinement in a common image plane, each of said imaging means being individual to one of said spaced images, and an obturator rotated once for each N picture cycle, said obturator having 2N+1 angularly spaced slots at proper radial distances to register one slot with each imaging means.

8. A motion picture apparatus comprising means for feeding framed motion picture film at uniform linear speed, a rotatable optical compensator arranged and adapted upon movement through five compensating cycles in timed relation with movement of the film through two picture frames to produce three successive stationary spaced images of a picture and two successive stationary'spaced images of the succeeding picture, five imaging means for re-imaging said spaced images in registering alinement in a common image plane, each of said imaging means being individual to one of said spaced images, and an obturator rotated once for each two picture cycles, said obturator having five angularly spaced slots at proper radial distances to register.

one slot with each imaging means.

JACOB F. LEVEN'I'HAL. 

